For the purpose of describing the invention, the material to be bagged and stored is assumed to be silage although other materials may benefit from the invention. Silage is a clingy type of material and does not readily flow. The conventional process of bagging silage involves placing of the silage material into a hopper of the bag filling machine where it is fed into a rotor at the inlet to a chamber referred to as a tunnel. The back of the tunnel is open and a bag secured to the tunnel receives material directed from the hopper and through the rotor into the tunnel.
Simply inserting the material into the bag is not satisfactory as the material will simply fill a bottom portion of the bag. Not only is such filling an inefficient use of the bag volume, but the loose-fitting bag is subject to easier tearing and the silage itself does not cure properly.
Previously, packing or compacting of the silage in the bag was accomplished by providing an adjustable backstop for the bag which releasably closes the end of the tunnel. The tunnel is designed to direct the flow of the material from the rotor to shove up against the closed end of the tunnel and then back fill the tunnel until it is completely filled. Further filling creates sufficient pressure to cause the backstop to release incrementally whereby the material compacted inside the tunnel is incrementally released into the bag.
The provision of the adjustable backstop involves considerable mechanism including cables that hold the backstop against the bag end, the cables being wound around drums mounted to the bag filling machine. The drums have brakes that resist unwinding of the cable but which release the cable when subjected to a predetermined pressure. An alternative to the use of a backstop as described above is disclosed in U.S. Pat. No. 5,297,377. In this patent, cables are positioned in the path of the material inside the bag and tunnel. The cables are anchored to each side of the tunnel and the material is simply pushed up against the cables. The cables interfere with free flow of the material but resistively allow the material to flow between the cables and within the bags.
Whereas the cables provide increased packing of the material as compared with a free flow condition, the arrangement has many defects. There is minimal control of how or when the materials flow through the cables. The cables being flexible will open up (become further spaced apart) in response to different flow forces which is but one of the disadvantages encountered.